Rate and attitude indicating instrument



Feb. 2, 1943. LYMAN ET 2,309,853

RATE AND ATTITUDE INDICATING INSTRUMENT Filed April 10, 1941 5 Sheets-Sheet 1 FMS-.1. F152 9 2 5 m FREQUENC- v 3 on 1 F Er 5 6-7 ;2 22 e I y 4 V Q INVENTORS JOSEPH LYMAN "mun ATTORNEY:

1943. J. LYMAN arm.

RATE AN; ATTITUDE INDICATING INSTRUMENT 5 Sheets-Sheet 2 Filfd April 10, 1941 F' I Er. E!

m M a OM N Tum R w m V T N. T A R OW JE H T Y B TO ATTITUDE INDICATOR Feb. 2, 1943 J. LYMAN EI'AL RATE AND ATTITUDE INDICATING INSTRUMENT Filed April 10, 1941 5 Sheets-Sheet 4 RN lY m SM w w Y ML W m D .A PO lwa m m E 0 H JE T .lllIll 1943- J. LYMAN El'AL RATE AND ATTITUDE: INDICATING INSTRUMENT Feb. 2

, 1941 5 Sheets-Sheet 5 Filed April 10 DETECTOR las PHASE DETECTOR FREQUENCY DOUB LER 0 F Er INVENTORS JOSEPH LY MAN NORDE together with -to provide a novel bratlng rod together with means for normally vibrating the same Patented Feb. 2, 1943 RATE AND ATTITUDE INDICATING INSTBUIHENT Joseph Lyman.

Pelham, N. Y.,

of New York Huntington, and Elwood Norden, assignors to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation Application April 10, 1941, Serial No. 887,810

28 Claims.

This invention relates, generally, to rate and attitude indicating instruments and the invention has reference, more particularly, to a novel instrument especially adapted for giving navigational information such as the heading of a craft with respect to the meridian or other reference. the rate of turn of a craft, and the attitude of a craft about the fore and aft and transverse axes thereof.

Heretofore it has been common to employ gyrosooplc instruments such as directional gyroscopes, turn gyroscopes and artificial horizontal gyroscopes for providing necessary rate and attitude indications for aircraft. In the present invention a vibrating rod or wire secured at one or both ends is employed for providing rate and attitude indications of movable craft, suitable electrical pick-off means being provided in connection with the vibrating rod or wire for picking-oif electrical signals for operating suitable indicators giving the desired information,

One object of the present invention is to provide a novel direction indicating instrument suitable for use. among other purposes, as upon a moving craft to indicate the heading of the craft with respect to the meridian or other reference.

Another object of the invention is to provide a novel instrument adapted to serve as a rate of turn indicator for showing the rate of turn about any desired axis.

Still another object of the invention is to provide means forrigidly mounting a rod' or wire at one or both ends and for vibrating the same, together with electrical pick-off means for producing potentials adapted to control a suitable indicating means. a

' A further object ofthe invention ls'toprovide a direction indicator comprising a winter rod member of U-shaped or substantially tuning fork form, the same being mounted for free turning about a central axis extending parallel to its arms and adapted to carry an angle indicator, means for vibrating the arms of said member, whereby said arms continue to vibrate in a fixed plane even though the case of the instrument be turned, thereby holding the angle indicator angularly stationary in space.

Still another object of the present invention is instrument employing a viinaa horizontal plane, said instrument having pick-oi! meansand an indi- A further object of the invention is to provide eator for indicating roll, and/or pitch of (the an instrument including a cathode ray tube having its deflecting plates excited by a version of the outputs from pick-oil coils associated with a horizontally vibrating rod, said cathode ray tube depicting on the face thereof an artificial horizon bar, the indications of which are similar to those of the standard artificial horizon.

Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings:

Fig. l is avertical section through a form of our invention useful asa directional indicator.

Fig. 2 is a fragmentary wiring diagram of, the same, showing the electrical connections to a Telegon type indicator.

Fig. 3 is a vertical section through a form of our invention useful as a rate of turn instrument.

Fig. 4 is a diagram of three vibration paths, useful in explaining the invention shown in Fig. 3 and Fig. M as modified.

Fig. 5 is a horizontal section through a form of our, invention employing a stretched wire clamped at both ends, which may be used as an attitude indicator.

Fig. 6 is an end view of the device shown in Fig. 5, together with a fragmentary wiring diagram showing a cathode ray indicator operated therefrom.

Fig. 7 is a verticalsection through a form of our invention useful as a directional indicator. 8 is a modification of the device shown in Fig. 9 is a horizontal section through another form of our invention which performs the functions of an artificial horizon.

Fig. 9A illustrates an adaptation of the stru ture of Fig. 9.

Fig. 10 is a detail of Fig. 9 taken at right angles to that figure.

Fig.llisasimpliiiedwiringdiagramusefui in explaining the device shown in Figs. 9 and i0.

Flg. lilisahorisontalsectionofanotherform oftzrur'invention useful as a rate of turn indica l'lgil3isanendviewofthesame device,showing a fragmentary wiring diagram of a dynamometer type indicator for use with said de-' vice.

Fig. 14 is a diagram of three vibration paths fled form of our rate of turn instrument illustrated in Fig. 3 and showing the use of capacity pick-offs.

Similar characters of reference are used in all of the above figures to indicate corresponding parts.

Referring first to Figs. 1 and 2, we have shown an outer casing I, within which is rigidly secured at its lower end in the mounting support or holder 21 a round rod 2, which therefore, is free to vibrate at its upper end and about its lower end as a center. The rate of vibration may be controlled by a mass 3 adjustably secured to the rod by a set screw. The vibration of the rod may be caused by an axial iron cored coil I through which pulsating or alternating current of approximately twice the natural frequency of the loaded rod is passed, the rod being preferably magnetically polarized. The plane of vibration of the upper end of the rod will remain fixed in space when the base 21 is rotated. The casing I may be pendulously mounted on a suitable universal support so that the base 21 thereof is normally maintained in an approximate horizontal plane. If the casing l tilts, the plane of vibration of the upper end of the rod 2 tilts corresponding thereto, the vibrating plane remaining constant with respect to the case. An evacuated glass envelope surrounding rod 2 and sealed by a metal to glass seal to base 21 is preferably empleyed to lessen air resistance and to remove any spurious eifects caused by air convection currents in the case I. It is to be,noted that the rod 2 may be caused to vibrate at the same frequency as that of the drlvingvoltage if the "rod is not magnetically polarized, although this is not a preferred inethod as it is somewhat ineflicient.

In order to furnish an indication of the path of movement of the rod, we have shown a plu-r the other hand a sub tanuaifi negligible n. u. r.

'willbegneratedinthepick-oifooilsiandt anglelthereto. hhould the tothcoutput ofamnl Wehaveshowninm repeater motor known to the art as the Telegon type. The stationary coil ll surrounding the z-shaped rotor or tumable magnetic core II of motor III is excited from the same A. C. source I! as excites the driving winding 5 through the frequency doubler 92. The output voltages of amplifiers i2 and it may also be used to operate a cathode ray tube in the manner shown in Fig. 6, or any other type of instrument which is capable of indicating the angle of the path of the free end of rod 2. Thus, in employing this device as a direction indicator as on a moving craft to take the place of adirectional gyroscope, the pointer II. which may have a friction drive or other adjustable connection with rotor I1, is initially set so that with rod 2 vibrating this pointer will indicate a desired reference direction such as magnetic north on the degree scale l8: Then as the craft is navigated the reading of pointer it with respect to the original scale setting of this pointer will furnish a continuous indication of the heading of the craft with re- =spect to magnetic north.

Fig. 3 illustrates our invention adapted to serve as a rate of turn indicator as for moving craft. A'magnetically polarized round rod 2 is symmetrically clamped in a base 28, and is excited by alternating or pulsating current supplied from leads 2'' and sent through oppositely disposed coils 20 and 2|,- adjustably mounted on yoke 23. The natural frequency of 'the rod 2 may be adjusted by means of the siidably mounted weight I to match the frequency of the exciting current. The rod 2 then vibrates in the plane defined by the axes of the exciting coils 20 and 21 which clearly distinguishes this form of the invention from that shown in Fig. 1. At right angles to this plane of vibration are placed two pick-ofl coils 24, one not being shown in the when the base 28 of the instrument is turned. as when the craft turns, gyroscoplc forces exertedbntherodcause the end ofthe rodto tend to precess in directions at right anglesto the axis-of the turning couple and at right angles iinedbytheaxesoffliedrivingcolls 2land2i, andthelengthofitsminoraxis tionallyrelatedtotherateofinrnofthehasefl, i.e.,of the craft. I'IgJIIIuehates theendoftherodmaytake entcirwmstanceathe turn. lmrlngaclock-wiseturnofthebasefl aglven rate,thepathof isillustratedbylithearrowsdmoting the ends direction of travel.

These components of s asoaess 3 the plane of at-rest vibration induce alternating tion is essentially the same as that of the device voltages in the pick-oi! coils 2d, the magnitude illustrated in Figs. 1 and 2. The wire 30 is of said voltages depending on the rate of turn shown as enclosed within a glass or other nonand their phaseupon the direction of turn, L e., magnetic tube 32, which is preferably evacuated the phase reverses with a reversal in the direc- 5 to reduce air resistance. Adjacent to the picktion of the turn. The phase reverses because of off coils 6', I, I! and 9 the tube is of reduced the fact that the direction that the end of rod 2 diameter so that the pick-off coils may be placed moves past the pick-off coils 2i reverseswhen the close to the wire. A magnetically polarized mass -craft on which the instrument is mounted it may be secured near the center of the'wire changes its direction of turn. The cores 24 are 10 to decrease the period of vibration, thus decreasrectangularly shaped and oriented as shown in ing the necessary length of the wire and making the drawing to produce a more nearly sinusoidal the instrument more compact.

output. These reversing phase, variable magni- Our invention is adaptable for use in still antude voltages may be fed from coils 2! into one other form as a directional indicator. Accordwinding of a dynamometer type meter as shown mg to this form, as shown in Fig. 'l, the vibratory in Fig. 13, the other winding of this meter being rod is shown as a U-shaped member 40, that is connected to leads w or these voltages may be preferably magnetically polarized, and may re fed into a thermionic phase detector to operate sembie a tuning fork clamped at its base in supa direct current meter. A phase meter of the port N, which, in turn, is rotatably mounted dynamometer type shown in Fig. 13 is more parabout a vertical axis in bearing members ll and ticularly disclosed on page 190 of the textbook H. The vibration of the tuning fork may be published in 1940 entitled "Electrical Measureeffected by circumferential three phase coil ll merits and Measuring Instruments" by E. W. excited by three phase alternating current from Golding. The device may be used to detect rate enerator 51. To spoke pieces extending from of turn about any axis when a suitable mounting he support 54 there may be secured a compass is provided. card it, visible through window l1 providing a Fig. 4A shows a somewhat modified structure reference mark cooperating with the indications wherein the vibrating rod I is directly observed of said card, and means may be provided for reat a point in its path preferably at an end of setting the same by pushing in setting knob 51 its minor axis. This is accomplished in Fig. 4A carrying a bevel pinion l9 thereon adapted to by use of a neon lamp 2! connected in the engage a bevel gear 48 on the compass card, the

' pulsating supply circuit leads 20". In order to knob 51 being pulled out and held by detent Iii adjust the point in the path at which lamp 24' after resetting. In this type of instrument,. the will illuminate the end of rod 2 the phase adtuning fork maintains its'plane of oscillation by justing circuit 25' is employed. The end of the means-of gyroscopic reaction. The instrument rod 2 may be colored as by use of white pigment is useful in any of the "three coordinates.

so that the same is more readily seen through Another means of driving the tuning fork type the slotted window 26' of the instrument 21'. of directional indicator is shown in the frag- In operation, when the craft makes a turn to men l? V w of F s- The coil 56 is rigidly the right the end of the rod 2 will appear to 40 attached to the base of the instrument and the move from opposite the central imiex 28' to the coil 55 to the rotatable shaft ii. The shaft right as one looks through the window ii' as being made of a magnetic material, the two shown inFig. 4A of the drawings. On the other coils and shaft act togethersas a transformer, hand, when the craft makes a turn to the left thus avoiding the use of slip rings and supply the end of the rod 2 will appear to move toward 5 ing alternating or pulsating en r to the the left, i. e., will be seen at the other end of the ing coils 52 and 53 from coil 55, coils I2 and 53' minor axis .of the path of motion of the free end i being mounted to rotate with the shaft 45.

of the rod shown in dotted lines in Fig. 4A. Our invention is also adapted to ike as an when the vibrating rod crosses the viewing slot artificial horizon, one such form being shown in at its extreme left or right position of move- Flgao, 10 and ii. In this form of the invention, ment, viewfl g h instrument 1 1 e fr m". round magnetically polarized rod) is clamped the same is'illuminated by lamp ll. Thus, the at one end in the casing I in a horizontal posioperator is enabled by dire ly ob rvin! h 1 tion and is vibrated by an A. C. or pulsating curstrument to determine whether or not the turn rent sent throrfgh a solenoid i. The plane of is to the right or to the left andthe distance of 55 oscillation of the rod 1 is normally maintained the spot indicating the end of the rod from the horizontal by electromagnets 8| secured to a central index 28' is a measure of the rate of bearing member l, which is rotatably mounted urn. on-boss ii on the interior of easing II in which B as- 5 and 6 s ow an ther type of directional rod 1 is secured. The axes of magnts ii are indicator employing a wire 30 which may be-of w normally maintained truly horizontal by a penmagnetic material Stretched b we $118 dulum 61 secured to said bearing member. so clamped end 35 and drum which that under normal conditions'the rod 2 vibrates the ire the We 5 The tension in a'horizontal plane and therefore generates may be by worm am no si pale in the ick-oif coils 50 and I f h worm pinion so from a thumb piece :4, thereby 5 apps becomesnmdmed, the 90mm. I i

adjusting the natural frequency of the wire to I H m 1m t! pick-off coils will be changed with respect to the that of the m mmuon plane of vibration of the rod, which plane is the wire ma be reduced b a three hase windmg a, mlied a; three g, megmm held horizontal by the stabilized magnets t1, and

mcbofls r. v, and m be therefore a signal will be generated in pick-off as n mg 2 t0 a and is B tunction 0f the Sine Of indicator. or the signal from the pick-offs may the angle of Thls 1m may be appliede applied t th deflecting plates 3., 31 r for visual observation to any of the aforemencathode ray tube 1| to give a visibleindication tioned indicating devices. This mstmment may of the path of vibration of the wire. The operab us in n o viou mann r to. indicate either 4- 2,309,858 roll or pitch in an aircraft, depending on the 91 and It. Whenever the aircraft's aspect angle manner in which said instrument is mounted. is altered, a direct t signal Dpcar-g on We have also shown a means in Fig. 10 for wires III, III, said being proportional to interrupting the excitation oi electromagnets ti ElEa cos a, where E1 is the voltage from transwhen the v cie on which the device is mounted 5 former I, and 0 is phase angle between makes a turn. Under such conditions, the total those two voltages. This direct urrent voltage acceleration forces on the pendulum will be is amplified by amplifier It, said amplifier slightly increased in accordance with the vector designed to amplify direct current as well as resultant oi the acceleration force oi gravity alternating current signals. and isapplied and the cen al acceleration force. As to the vertical plates of cathode ray tube l. shown, the pendulum bob I1 is secured to a sleeve Knobs lit and I provided on amplifiers 66 slidably mounted on a stem ii, the mass of it and 95. respectively, to furnish means for the pendulum being normally just balanced by adjusting their outputs. the coil spring 6 Therefore in the presence Another form of turn indicator type of instruof acceleration forces, the pendulum bob will ment is shown in Figs. 12 mid-i3. In these figmove downwardly slightly and thus break conures the rod is shown as a fiat m tacts 89, one of which is secured to the penduolarized strip 12 clamped near one end in a lum hob and the other to the fixed stem It. Said bearing member 13 so that the flat surface of contacts are normally in series with the coils 8| the rod is horizontal. Member II is bly and when opened interrupt the restraint exerted mounted in a bracket within casing II. By fiaton the vibrating rod by the coils 6 The edect tening the strip and by using a cen ralizin of this interruption is to provide a means i'or spring 15 extending between the short end oithe ave aging out normal turn errors. There may be rod and bracket T4, a vertical plane of tion placed two pick-01f coils 8! at right angles to is predetermined. A coil ll supplied with alterthe coils I! and 68, as indicated by dotted lines nating or pulsating current is shown for the purin Fig. 9, to use of the instrument as part of an pose of vibrating the strip Upon turn of the attitude indicator to register pitch and roll of craft, the plane of vibration of the end of the an aircraft as shown in Fig rod will depart from a vertical plane and become In Fig. 9A we produce on the screen of the a figure eight as shown at B in 14. The cathode ray tube It a line I08 whose position amplitude and phase of the vibration again are the vertical direction depends upon the angle functionally related to the rate of turn and to of pitch and whose armle to the horizontal index the sense of turn, respectively. Due to the disline ill marked on the face of the tube indicates symmetry in stifi'ness of the flat rod the clamped the angle of roll. This sheet is produced by the end of the rod will twist with the same frequency foll means. of vibration with which the other end of the rod For indicating pitch we have shown schemativibrates back and forth. The behavior of the cally an instrument Hi6 like that of Fig. 9, with rod under these circumstances may he arrived no horizontal pick-oil coils 93, but with two verat from obvious analysis somewhat to tically mounted pick-oil coils 59" and t0", the that used in discussing the rod 2 of Fig. 3. device being mounted so that the end of the rod 40 As a pick-ofl for this type of instrument, we 2 vibrates for normal level flight in a direction have shown a downwardly extending permanent parallel to the direction of flight of the aircraft magnetic member 11 secured to the short end For indicating roll, we employ another instruof rod 72 On each side of the lower end of the ment ll! like that of Fig. 9 which has pick-on magnetare shown pick-oil coils II and It. When coils mounted horizontally (83') as well as vertithe aircraft is at rest or moving uniformly in a cally (59', it) This instrument is mounted so straight line, the magnetic pole ll of the magthat its rod 2 vibrates in a horizontal line at right net I1 will remain stationary, but upon turn of angles to the line of vibration of the free end the craft it will be oscillated between the pick-oi! oi the rod 2 in instrument I06 e rods are coils at a frequency equal to the mummy of driven by means of power supplied from genthe vibration of the rod 12 with an amplitude erator illl through frequency doubler 32' to exproportional to the rate of turn and a phase deciting coils 5' and I". pending on sense of turn. suitable form of From the roll axis instrument I05, alternating indicator may be actuated therefrom such as a voltages which appear in pick-oi! coils 58' and left-right turn indicator I. which is a hero cen- 6 are applied to the vertical plates of cathode ter amometer type meter. As is well kno ray tube to through amplifier 5 Alternatin in the art, coil 88 of this meter is fixed and may voltages which appear in the coils 93' are applied be supplied with the same frequency as the drivthrough amplifier 84 to the horizontal plates of ing coil Ill; and coil 82, to which the indicator the cathode ray tube. Thus, when rod 2 of roll needle is fastened takes up a position according axis indicator illi is vibrated a straight line trace 60 to the amplitude and phase (with respect to the appears on the cathode ray tube screen. From phase of source 8|) oi the voltage generated by previous discussion of Fig 9, it is evident that the pick-oil coils 18 and ll. the angle said trace makes with index mark Ill Fig. 15 shows a modification oi the rate of on the face of the screen then indicates to the turn instrument of Fig. 3 adapted for use with pilot the angle of roll. capacitive pick-offs in place of the el ctromag- As is well known in the art, the pitch angle netic pick-oil's 24 shown in 3. Referring to is usually indicated by the distance of the center Fig. 15, the rod 2 is driven by power supplied to of trace ill above or below index Ill, appearing above the index when climbs.

IE8 is mounted to provide this indication. The coils 59" and 60" is, by means of the electronic phase detector I08, compared in phase with a signal from generator I through transformer" ill, by means of diodes 75,

exciter coils 20 and If thmh frequency doubler I20 from generator iii. The theory of operation of the rod 2 is exactly that described in iscussour invention as a Asmany changes could made without departing from "orwirode the capacity between plates I22 and I23 to that between the plates I22 and I24 is a constant. It the craft makes a turn, the path oi the end of rod 2 opens into an ellipse, and plate I22 then has an alternating component of motion such that this capacity ratio varies with a frequency equal to that of the rod 2.

An alternating current bridge is employed and is made up of these two capacities and the con; densers I21 and variable so that the ratio of the capacities of condensers I28 to I21 may be made the same at theratio of the capacities between plates I22 and I23 to that between plates I22 and I24 for straight line vibration of the rod corresponding to straight flight. To one set of midpoints of this bridge is applied an alternating current of the frequency 1' (on the order of 10,000 cycles) generated by oscillator I25 and fed through transformer I28. As long as, the rod vibrates in a straight line parallel to the plates, the bridge remains balanced; but when the pick-oil! capacity ratio varies due to a turn of the craft, the frequency I modulated by the frequency of the rod 2 appears at the other midpoints of the bridge and is placed across series esistors I29 and I30. By means of triodes I22 and Ill, this signal is amplified and fed to the detector circuit I35, which removes the frequency 1 signal, leaving a low frequency voltage: The magnitude of this low frequency voltage depends upon the rate of turn of the craft and its phase upon a the direction of the turn.

The phase detector I28 operates in a similar manner to'that shown as circuit I09 in Fig. 9A. In phase detector I", the reversing phase low frequency signal voltage is compared to the phase of the standard signal provided by generator. III. The indicator I31 may be any of the devices suggested for operation with the instrument shown inFig.3. Thedeviceisusefulinanyofthe three coordinates, providing suitable mounting is provided.

Also, while we have not heretofore referred to gyroscope since the motion of the oscillating mass is vibratory rather than continuously rotational, apparatus constructed in accordance with our invention seems to posses marworthepropertiesof pesanditis probably not incorrechthereiore, to refer to the invention as a vibratory gyroscope.

be made in the above apparently widely difthis invention could be the scope thereof, contained in the construction and many ferent embodiments-cf it is intended that all matter above description or shown in the accompanying drawings shall be interpreted, as illustrative and not in a limiting sense. i

What is claimed is:

1. In a rate oi! turn-instrument, a support. a rod carried by said support, means for vibrating said rod in a plane. and electrical pick-oil means positioned adjacent said vibrating rod for producing potentials responsive to-movements of said A red departing from vibration in said plane.

2. In an instrum scribed, a support, a or'wire carried by said support, electrical means for vibrating said rod or wire,- electrlcal pick-oi! means positioned adfrom indicating means controlled'from said pick-oi! means.

vibration in a plane, and the output of I28. The condenser I20 is madeof the character deboth ends, a driving rounding said wire,said .75. energized with alternating current for vibrating and free to vibrate at its other end, electromag- I netic means for vibrating the free end 01 said rod at substantially the natural frequency thereof, pick-oil coils disposed about said rod for generating potentials responsive to the path of vibration thereof, and a direction indicator controlled from the outputs-of said pick-oi! coils.

4. In a direction indlca eat, a support, a rod or wire carried by said support, means for vibrating said rod or wire in a plane, and electrical pick-oi! means positioned adjacent said vibrating rod'or wire for producing potentials responsive to movements of said rod or wire dearting from vibration in said plane responsive to movements of said pick-oi! means with respect to said plane of vibration of said rod. 5. A direction indicating instrument comprising a substantially vertical rod supported at one,

end andi'ree to vibrate at its ing source of current supply, a magnet coil disposed adlacent the free end of said rod in substantial alignment with the vertical :axis thereof and excited from said source for vibrating said rod, two pairs of pick-oi coils surrounding said rod and disposed substantially at right angles to one another, an indicatorhaving crossed stator windings connected respectively to be energized with a version of the output of a respective pair of said pick-oi! coils, said indicator having a rotor provided with a winding excited from said source, and direction indicating means actuated by saidrotor.

6. A rate of turn indicatin instrumentcomprising a substantially vertical rod supported at one end and free to vibrate at its other end, a varying source oi current supply, clectro-magnetic coils disposed on oppositesides of said rod and excited from said source for vibrating said rod in a desired vertical plane, pick-oil coils disposed on opposite sides of said rod at right angles to said vibrating coils for producing potentials ive to motion of the rod at right angles to its plane oi! vibration between said vibrating coils, and an indicator having a winding excited by a version of the output oi! said pick-oil coils and another winding excited from said source,

relatively movable. of the character described, a rod or wire, means for supporting said rod or wire, electromagnetic means fed from said source and arranged for vibrating said rod or wire, and means for loading said rod or wireso that its natural frequency is made a function of the frequency of said source. A

8. In a direction indicator, a wire secured at both ends, electromagnetic means for vibratin said wire, an electrical pick-oil. disposed adjacent other end, a varysaid wire, and a direction indicator controlled from said pick-oil.

9. In a dlrectionindicator, a wire secured at coil. surrounding said wire. said coil being arranged to be energized with alternating current for vibrating said wire, means for varying the tension of said 'wire so that its natural frequency will substahtially conform to that of said alternating current, two pairs of pick-oil coils disposed at right angles to one another about said wire, and an indicator controlled from said pick-oil coils.

10. In a direction indicator for movablecraft,

a wire secured at both ends, a driving coil surcoil being arranged to be pick-oi! coils to one pair saidwire,meansforvaryingthetensionofsaid wire so that its natural frequency will substantially conform to that of said alternating current, two pairs of pick-R coils disposed at right angles to one mother about said wire, a cathode ray tube having deflecting I plying a version of the output of one pair of said of said plates, and means for supply n a version of the output of the other pair of said coils to the other pair of deflecting plates of said tube, whereby the oathoderaybeamofsaid tubeiscaused todrawa line the direction of which varies with change in course.

11. In a direction indicator, a U-shaped rod member having two vertical legs and a transverse connecting portion, a turnable support for said rod member connected to said transverse portion substantially midway between said legs, means for vibrating the legs of said member in a common plane, and a compass card carried by said tmnable support.

12. In a direction indicator, a U-shaped rod member having two vertical legs and a'transverse connecting portion, a turnable support for said rod member connected to said transverse portion substantially midway between said legs, electrical means for vibrating the legs of said member in a common plane, a compass card carried by said turnable support, and means for turning said compass card and said support for setting up a desired course.

13. Means for indicating roll or pitch of a craft comprising a substantially horizontally disposed rod supported at one end and free to vibrate at its other end, means for vibrating said rod and for normally maintaining the plane of such vibration horizontal, pick-oil coils disposed adjacent said rod, and indicating means controlled from a version of the outputs of said coils.

14. Means for indicating roll or pitch of a craft comprising a substantially horizontally disposed rod supported at one end and free to vibrate at its other end, means {or vibrating said rod, pendulously controlled means for normally maintaining the plane of vibration oi said rod horizontal, means for nullifying the operation of said pendulously controlled means during turning movements for averaging out turn errors, pick-oil coils disposed on opposite sides of said rod, and an attitude indicator controlled from the outputs of said pick-off coils.

15. An instrument for indicating pitching of a craft comprising a rod supported at one end for extending substantially transversely of the craft, a driving coil excited by varying current disposed adjacent the free end of said rod for vibrating said rod, pendulously controlled electromagnetic means for confining the vibration of said rod'in a direction substantially parallel to the direction of flight of the craft, pick-oil coils disposed above and below said rod, andlndicating means controlled from the outputs of said coils. 7

16. An instrument for indicating rolling of a craft comprising a rod supported at one end for extending substantially fore and aft of the craft, a driving coil excited by varying current disposed adiacent the free end of said rod for vibrating said rod, pendulously controlled electromagnetic means for confining the vibration of said rod in a direction substantially at right angles to the direction of flight of the craft, two

pairs of pick-oil coils disposed at right angles to one another around said rod, and indicating means controlled from the outputs of said coils.

plates, means for sup- V of said mass in some pattern,

17. An artificial horizon indicating instrument for aircraft comprising a pair of rods fixed at one of their ends and free to vibrate at their other ends, means for vibrating said rods horizontally, pick-oil coils disposed about said vibrating rods, a cathode ray tube having deflecting plates, and means for applying versions of the outputs of said pick-oh calls to the deflecting plates of the cathode ray tube to produce an artificial horizon line movable in response to rolling and pitching of the craft.

18. A turn indicator for aircraft comprising a flat rod extending substantially horizontally and rotatably supported at one point along its length for turning about a horizontal axis, a centrallizingspring connectedtosaidrodandtoarelatively fixed support, means for vibrating said rod in a vertical plane, pick-oil. means associated with said rod and an indicator operated from said pick-oi! means.

19. In a rate oi turn alternating current, means fed from said source for vibrating the other end of said rod in a plane, a bridge circuit including capacity pickofl means extending adjacent said rod, 9. phase detector connected for comparing the phase of said source with the O tput of said bridge circult, and an indicator controlled from said phase detector.

20. In -a rate oi turn instrument, a support, a rod or wire carried by said support, means for vibrating said rod in a plane and stroboscopic means for directly indicating departures of said rod from its plane of vibration.

21. A vibratory gyroscope comprising a pivoted mass, means for causing continuous vibration and means for indicating departure of the path of movement of said mass from said pattern.

22. A vibratory yroscope comprising a pivoted mass, means for causing continuous vibration or said mass in a plane. and means for indicating the direction and amount of departure of the vibratory movement of the mass from said plane.

23. A vibratory oscope of the rate of turn class, comprising a rod clamped at one point. means for vibrating-said rod about one horizontal axis whereby, upon turn of the craft, precession will cause vibration also about a second axis, pick-ofl' means for detecting such change in the path of vibration, and a turn indicator operated from said pick-oi! means.

24. A vibratory gyroscope of the directional gyroscope type. comprising a rod, mounting horizontal axis, means for mounting the clamp for free movement about a vertical axis, and means for continually vibrating the free end of said rod without coercing the same in any plane.

25.A vibratory gyroscope of the directional and a self-synchronous retion of which is journaied for turning about a plane of vibration of said rod, and an attitude vertical axis. indicator actuated by the output oi said pick-oi! 27. An attitude indicator for aircraft oomprismeans.

ing a fixed suppo a vibratory rod clamped 28. An attitude gyroscope of the vibratory thereon at one point, magnetic means ior co- 5 type, comprising a pivoted mass, means for fixercing said rod to cause it to vibrate in a deiing the normal vibration thereof in a horizontal inite plane, a pendulous member for stabilizing plane, and means for indicating a change in said means whereby a force is exerted on said the path of movement of said vibratory means. rod to change its plane of vibration upon relative tilt of said pendulous means and support, 10 JOSEPH LYMAN.

pick-oi! means responsive to changes in the ELWOOD NORDEN. 

